In position detection with respect to a linear motor car or the like, signal processing is conducted to obtain a position detection signal. In the signal processing, two-phase sine wave with a phase difference of ninety degree outputted from a sensor unit is utilized.
A signal processor including a counter and an AD-convertor has been conventionally utilized to digitally process such the signal processing. In the signal processor, the counter counts an edge of the binary two-phase signal and the AD-convertor converts a signal level of the two-phase signal between the edges.
In the signal processor, a period of one count of the counter is interpolated by output data of the AD-convertor, so that a position detection resolution can be improved.
However, an AD-convertor processing by the AD-convertor generally consumes time. Therefore, an output from the AD-inverter is delayed not to correctly count value transformation of the counter in the binary two-phase signal. Accordingly, it has been a problem that the count value of the counter may be not correctly interpolated.